1. Field of the Invention
This invention relates to slide fasteners and has particular reference to a slide fastener having a support tape made of a fabric material free of threads woven or knitted.
2. Prior Art
There are known slide fasteners which comprise a support tape carrying along its one longitudinal edge a row of coupling elements, the support tape being made of a film of synthetic resin, a non-woven fabric or a thread-free material similar to a material used for the marginal edges of an opening in an article such as a bag to which the slide fastener is attached. It has thus been desired to use physicochemically similar or compatible materials for slide fastener tapes and for at least portions of an article to which the slide fastener is attached. Heretofore, rows of coupling elements were secured to the support tapes by means of sewn seams consisting of multifilamentary threads as such multifilament would yield itself to the contour of the coupling element and thus give rise to positional stability of the coupling element. It was however necessary subsequently to heat-set a finished slide fastener chain in order to cause this chain to become thermally contracted thereby stabilizing the attachment of the coupling elements to the support tapes.
It has been found that during heat-setting of the fastener chain, the multifilament, threads 7 undergo considerable deformation as shown in FIGS. 5 and 6; that is, the multifilament threads 7 having substantially round cross-section (FIG. 5) prior to application of heat become flattened (FIG. 6) after heat-set, with sharp edges extending transversely across the support tape 8 and forcing the perforated seam 9 of the tape 8 to deform in conformity with such sharp edges of the multifilament threads 7. When transverse pull is applied to such slide fastener, the web of the tape 8 tends to become ruptured at and along the perforated seam 9 that has been deformed, loosening up the connection between the multifilament threads and the coupling elements (not shown) and finally rendering the fastener useless.